The present invention relates to a method and apparatus for suspending, cementing and packing off a liner within a well, and more particularly to a one trip liner hanger and packer, and still more particularly to a setting tool for setting the packer within the well, and most particularly to setting the packer by hydraulic and/or mechanical means and releasing the setting tool from the packer.
Typically, in the drilling of a well, a borehole is drilled from the earth's surface to a selected depth and a string of casing is suspended and then cemented in place within the borehole. A drill bit is then passed through the initial cased borehole and is used to drill a smaller diameter borehole to an even greater depth. A smaller diameter casing is then suspended and cemented in place within the new borehole. Generally, this is repeated until a plurality of concentric casings are suspended and cemented within the well to a depth which causes the well to extend through one or more hydrocarbon producing formations.
Oftentimes, rather than suspending a concentric casing from the bottom of the borehole to the surface, a liner may be suspended either adjacent the lower end of a previously suspended and cemented casing or from a previously suspended and cemented liner. The liner extends from the previously set casing or liner to the bottom of the new borehole. A liner is casing which is not run to the surface. A liner hanger is used to suspend the liner within the lower end of the previously set casing or liner. Typically, the liner hanger has the ability to receive a tie back tool for connecting the liner with a string of casing which extends from the liner hanger back to the surface. Liners may be used for both land and offshore wells.
A setting tool disposed on the lower end of a work string is releasably connected to the liner hanger which is attached to the top of the liner. The work string lowers the liner hanger and liner into the open borehole extending below the lower end of the previously set casing or liner. The borehole is filled with fluids such as drilling mud which flows around the liner and liner hanger as the liner is run into the borehole. The assembly is run into the well until the liner hanger is adjacent the lower end of the previously set casing or liner and the lower end of the liner is above the bottom of the open borehole. As can be appreciated, it is desirable to have the inside diameter of the liner be as large as possible to allow more space for additional liners to be disposed within the well.
When the liner reaches the desired location relative to the bottom of the open borehole and the previously set casing or liner, a mechanism in the setting tool is actuated to move slips on the liner hanger from a retracted position to an expanded position into engagement with the previously set casing or liner. Thereafter, when weight is applied to the hanger slips, the slips are set to support the liner.
The liner hanger setting tool may be actuated either hydraulically, or mechanically. See U.S. Pat. No. 4,712,614. The setting tool can have a hydraulically operated setting mechanism for the hanger slips or can have a mechanically operated setting mechanism for the setting slips. A hydraulically operated setting mechanism typically employs a hydraulic cylinder which is actuated by pressure in the bore of the work string. In mechanically setting the liner hanger, it is usually necessary to obtain a relative downhole rotation of parts between the setting tool and liner hanger to release the hanger slips. The hanger slips are then one-way acting in that the hanger and liner can be raised or lifted upwardly but a downward motion of the liner sets the slips to support the hanger and liner within the well.
Then to release the hanger, the setting tool is lowered with respect to the liner hanger and rotated to release a running nut on the setting tool from the liner hanger. Cement is then pumped down the flowbore of the work string and liner and up the annulus formed by the liner and open borehole. Before the cement sets, the liner hanger setting tool and work string are removed from the borehole. In the event of a bad cement job, a liner packer and liner packer setting tool are then attached to the work string and lowered back into the borehole. The packer is set utilizing the liner packer setting tool.
Packers for liners are often called liner isolation packers. A typical liner top isolation packer system includes a packer element mounted on a mandrel. A seal nipple is disposed below the mandrel which stings into a tie back receptacle on top of or below the liner hanger. A liner isolation packer is used to seal the liner in the event of a bad cement job. Typically, the liner isolation packer is set down on top of the hanger and the packer is set by a setting tool to form a seal of the annulus between the liner and the previously set casing or liner.
Another problem occurs if the cement extends over the top of the liner before the packer is run into the well. If that occurs, it is necessary that the operator run into the well and remove all cement from the sealing receptacle of the liner hanger which receives the packer.
The above process requires additional trips into the well. It is preferred to eliminate these additional trips. This requires that the packer and packer setting tool be lowered into the well with the liner hanger and liner. By having a single trip operation, the potential of damaging the formation during the additional trips into the hole are avoided. In a one trip system, the hanger and packer are run into the wellbore together until the desired location is reached. The hanger is then set and the setting tool nut is disengaged from the hanger. The setting tool is supported by the work string with a sealing device in the bore of the liner hanger so that there is a continuous bore from the earth's surface to the lower end of the liner. When cement is pumped through the continuous bore formed by the work string, liner, and cementing equipment, the cement is displaced up the annulus between the liner and open borehole. Following the cementing of the liner in the borehole, the liner packer is set and the liner hanger and packer setting tools are retrieved and the drilling or completion operation continued.
Some prior art systems do not separate the packer setting mechanism from the hanger setting mechanism. Thus, the packer may be set prematurely in attempting to set the liner hanger.
Prior art combination setting tools must be concerned about the passage of pressures into the setting tool which would either set the packer or release the liner hanger. One trip systems typically rely upon stacked shear pressures for hydraulically setting the liner hanger and packer or a separate dog section for mechanically setting the liner packer. Setting tools that rely upon stacked shear pressures to sequentially set the hanger, cement, and then set the packer, are subject to pressure surges or spikes that can prematurely set the packer. Also, hydraulically set equipment often requires that shearing take place and sometimes the shear mechanism shears prematurely or won't shear at all. Further, a separate dog section for mechanically setting the packer is not as effective in horizontal wells since limited set down weight can be applied to the dogs. Prior art combination setting tools limit the variety of operations to set the liner hanger due to the possibility of also setting the packer prematurely.
In deep wells, most liner hangers and packers are set hydraulically rather than mechanically. Particularly if the mechanical set requires a rotation of the work string. In deep wells, it is difficult to rotate the lower end of the work string because of its length. Further, even if the work string is rotated, the operator may be unsure whether that rotation was translated to the liner hanger, packer or work string.
Many prior art liner hangers, packers and setting tools do not allow the operator to have the option to either set hydraulically or mechanically. Further, those systems that allow both hydraulic and mechanical operation require a particular sequence of operation such that the system will allow the liner hanger to be set mechanically and then allow the packer to be set hydraulically.
The present invention overcomes the deficiencies of the prior art.